This invention relates to means for joining together two tubular bodies, primarily those used during percutaneous transluminal coronary angioplasty (PTCA). More particularly, this invention relates to means for joining an extension wire to a guide wire to facilitating catheter exchanges during angioplasty.
Those skilled in the art of PTCA know that it is frequently necessary, during an angioplasty procedure, to exchange balloon catheters. Most commonly this is done to exchange a catheter having a balloon of one size for one having a balloon of a different size.
Normally, PTCA catheters are inserted over guide wires. The guide wire may be inserted first, followed by the catheter, or alternatively, the two may be assembled outside the body and then inserted as a unit. The guide wire is typically between about 20 and 50 cm. longer than the catheter. The guide wire, either as part of the assembled unit, or separately, is fed up through the arterial tree until its distal tip has passed through the stenosis to be opened. Generally, the distal tip of the guide wire is provided with a radiopaque marker so that the physician can determine, using fluoroscopy, its location within the body. Once the guide wire is in place, the PTCA catheter is advanced until its balloon is within the stenosis. Typically, the PTCA catheter is also provided with radiopaque markers at its distal end so that the location of the balloon can be confirmed under fluoroscopy.
Often the first PTCA catheter must be removed and replaced with another. The need for an exchange may arise because the first balloon selected is too large to enter the stenosis and a second, smaller balloon must be substituted for it. The need for the exchange may also arise because the first balloon, while small enough to enter the stenosis, is not large enough to open the lumen sufficiently to provide adequate perfusion. A second, larger balloon must then be substituted for the first to open the lumen further.
Once the physician has been successful in having the guide wire negotiate the often tortuous path to the lesion, it is important that the path to the lesion be maintained during balloon exchange. One way this has been accomplished in the past is by replacing the guide wire with a much longer exchange wire. To do this, the guide wire is first removed, leaving the catheter in place. The guide wire is then replaced with a much longer exchange wire. During this procedure, the first catheter remains in place, providing a channel for the exchange wire to follow to the lesion, hence the exchange wire need not negotiate the path anew. The first catheter can then be removed and the second one inserted over the exchange wire without ever losing control over the wire.
Once the exchange has been made, however, it is generally considered highly desireable not to have the long proximal end of the exchange wire extend from the catheter. It is very unwieldy, it gets in the way during the subsequent angioplasty procedure, it can fall and drag on the floor, getting dirty and contaminated and is generally at the very least a nuisance. Therefore, another exchange is often performed, this one to replace the exchange wire with a much shorter guide wire.
Another method that has been used to substitute one catheter for another without losing control over the wire involves attaching a guide wire extension to the proximal end of the guide wire. One means of attaching such an extension wire is shown in U.S. Pat. No. 4,917,103 in which the two wires are attached by means of a crimping action. Although this method provides for a reasonably secure junction, it makes it very difficult to detach the two wires when the exchange has been completed.
A second means for attaching the extension wire to the guide wire, as described in U.S. Pat. No. 4,827,941, involves the use of a tubular connector. This connector is fixedly attached, at one end, to the extension wire, and is adapted to receive the guide wire into its other end. The diameter of the guide wire opening in the connector of the '941 patent is larger that the portion of the guide wire to be inserted therein. The guide wire, therefore, is provided with an undulating proximal end, the diameter of which, as measured from upper peak to lower peak, being greater than the inside diameter of the connector. Because of these undulations, when the guide wire is inserted into the connector, a friction fit is assured, with contact being made between the peaks of the undulations and the inside wall of the connector.